cladistics(redirected from Plesiomorph)
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n. (used with a sing. verb)
A system of classification based on the presumed phylogenetic relationships and evolutionary history of groups of organisms.
cla·dis′tic, cla·dis′ti·cal adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
cladisticsan approach to CLASSIFICATION by which organisms are ordered and ranked entirely on a basis which reflects recent origin from a common ancestor, i.e. like a family tree. The system is concerned simply with the branching of the tree and not with the degree of difference. The latter is the concern of evolutionary taxonomists who oppose the cladistic approach.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005